Hi,
The kernel oops[1] is triggered during kernel boot with the latest next
tree(3.11.0-rc5-next-20130816), looks it is caused by reference to uninitialized
percpu ref of root cgroup, and below patch can fix the problem:
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 723194f..0e8954b 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4485,7 +4485,8 @@ static long cgroup_create(struct cgroup *parent,
struct dentry *dentry,
struct cgroup_subsys_state *css = css_ar[ss->subsys_id];
dget(dentry);
- percpu_ref_get(&css->parent->refcnt);
+ if (!(css->parent->flags & CSS_ROOT))
+ percpu_ref_get(&css->parent->refcnt);
}
/* hold a ref to the parent's dentry */
[1], oops log:
[ 3.155985] Unable to handle kernel paging request at virtual
address 011bb000
[ 3.163083] pgd = ee864000
[ 3.165715] [011bb000] *pgd=00000000
[ 3.169219] Internal error: Oops: 5 [#1] PREEMPT SMP ARM
[ 3.174428] Modules linked in: ipv6
[ 3.177844] CPU: 1 PID: 1 Comm: systemd Not tainted
3.11.0-rc5-next-20130816+ #237
[ 3.185280] task: ef00e400 ti: ef09c000 task.ti: ef09c000
[ 3.190573] PC is at cgroup_mkdir+0x324/0x5a0
[ 3.194841] LR is at cgroup_mkdir+0x314/0x5a0
[ 3.199114] pc : [<c00742c8>] lr : [<c00742b8>] psr: 40010013
[ 3.199114] sp : ef09def8 ip : 00000000 fp : ee8e0000
[ 3.210393] r10: c064b4e4 r9 : ef09c000 r8 : c064b528
[ 3.215511] r7 : c064b4dc r6 : ee8e0018 r5 : eed1f880 r4 : eebf2c00
[ 3.221918] r3 : 011bb000 r2 : ef09de78 r1 : 60010013 r0 : 00000030
[ 3.228326] Flags: nZcv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user
[ 3.235329] Control: 10c5387d Table: 6e86406a DAC: 00000015
[ 3.240964] Process systemd (pid: 1, stack limit = 0xef09c238)
[ 3.246687] Stack: (0xef09def8 to 0xef09e000)
[ 3.250956] dee0:
000000d0 eef837f8
[ 3.258993] df00: 180fb270 00000000 eeb75023 ee8e000c eed1f8d4
ee8e0130 00000000 00000000
[ 3.267020] df20: eea1fa80 ef0de880 00000000 00000000 00000000
00000000 00000003 00000000
[ 3.275049] df40: eefe2d70 eed1f880 000001ed ffffff9c ef09c000
0011be80 be9814ac c00ec0bc
[ 3.283077] df60: eefe2d70 eed1f880 000001ed eed1f880 00000002
000001ed 00000027 c00efb74
[ 3.291106] df80: ef2ebc10 eef837f8 000001ed 0011be80 000001ed
000cc730 00000027 c000e048
[ 3.299135] dfa0: 00000000 c000dea0 0011be80 000001ed 0011be80
000001ed 00000001 00000000
[ 3.307164] dfc0: 0011be80 000001ed 000cc730 00000027 000d7202
ffffffef 0011be80 be9814ac
[ 3.315192] dfe0: 000cc03c be9813bc 00055280 b6d6769c 60010010
0011be80 fffdffff ffffffff
[ 3.323225] [<c00742c8>] (cgroup_mkdir+0x324/0x5a0) from
[<c00ec0bc>] (vfs_mkdir+0x88/0xc8)
[ 3.331424] [<c00ec0bc>] (vfs_mkdir+0x88/0xc8) from [<c00efb74>]
(SyS_mkdirat+0x6c/0xa0)
[ 3.339369] [<c00efb74>] (SyS_mkdirat+0x6c/0xa0) from [<c000dea0>]
(ret_fast_syscall+0x0/0x30)
[ 3.347821] Code: e59dc00c e31c0003 1a000004 ee1d3f90 (e793200c)
[ 3.353817] ---[ end trace ea0a2516971df41f ]---
Thanks,
--
Ming Lei
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